Emma thomas laxton clark



UNITED STATES PATENT ErrcE.

EMMA THOMAS LAXTON CLARK, OF LONDON, COUNTY OF MIDDLESEX, ENGLAND.

PROCESS OF HARDENING AND PRESERVING PLASTER-OF-PARIS CASTS AND MOtDS AND MAKING THEM IMPERVIOUS T0. WATER, &c.

SPECIFICATION forming part of Letters Patent No. 371,550, dated October 18, 1887.

Application filed March H, l8 .7. Serial No. 230.866. (No specimens.) Patented in England July 23, 1886, No. 9,536.

To ctZZ whom it may concern:

Be it known that I, Erma Tno'rms LAXTON CLARK, of London, in the county ofMiddlesex, England, fine-art molder, asubject oftheQueen of Great Britain, have invented a certain new and useful Improved Process for Hardening and Preserving Plasterof-Paris Casts and Molds and Making Them Impervious to WVater and Rendering Unnecessary the Ordinary Process of Whitewashing or Painting, (for which I have obtained Letters Patent in Great Britain, No. 9,536, July 23,1886;) and I do hereby declare the following to be a full, clear, and exact description of the invention.

My invention relates to ornamental casts or ornaments used for architectural and building purposes, such as ceiling cnrichments of the most elaborate character, statues, statuettes, and busts.

Molds made solely of plaster-of-paris (sulphate of lime) can by my invention be so strengthened that casts can be taken from them.

Casts to which my improved processes are to be applied must be made solely of plasterof-paris, without any other admixture, and preferably free from dirt or stain. By niyinvention such casts are made hard, strong. and durable, their original beauty being retained and added to, and when made of fine plasterof-paris they are capable of receiving a very high polish. They then have the appearance of statuary marble, but are more impervious to water, and will therefore last longer without discoloration.

Casts treated according to my processes are not so liable to injury by dirtand atmospherical changes as most of the natural or artificial stones now in use, for they can be easily cleaned by washing with soap, hot or cold water, and sponge or brush, rendering unnecessary the ordinary method of whitewashing or paintingas now practiced for ccilingenrichmeuts, statues, statuettes, and busts and objects of the like kind, thus-enabling them to retain their original beauty.

Casts, after having gone through my processes, are fitted for external as well as internal use or decoration.

The following is a description of my inven tion:

First. I use a novel hardening process, which consists in immersing the casts or molds, made solely of plaster-of-paris, in a bath containing a solution of boraX, (biborate of soda.) This I apply in the proportion of about one pound to every gallon of boiling water. All the articles to be treated should be quite dry at the time of immersion. \Vhen it is required that casts should be made extra hardas, for i11- stance, for external use-the aforesaid solution should be used while still hot; but when a slighter induration or hardness is sufficient the casts should be immersed in the same solution when cold. This will be a saving both of time and material, as the cold bath will suffice for those objects intended for internal use or decoration. The length of time of the immersion must vary according to the porosity and thickness of the articles to be treated that is to say, for casts one inch thick from fifteen minutes to half an hour are sufficient, whereas casts of from six to twelve inches would require to be immersed in the boraX solution for from one to two hours. The test for ascertaining whether the casts are fully indurated is that it any article on being taken out of the solution in the bath has not received as much of the solution as it can ab sorb it will quickly appear to be dry on the surface; but if it cannot take up any more it will remain wet on the surface and will drip, which will be a proof that the cast is fully indurated. After the casts are taken from the bath, it is necessary that they should be immediately dried, which is best accomplished by placing them in a room heated by artificial heat, the range of temperature being from about 90 to 140 Fahrenheit. This first process, as fully described above, is quite complete in itself for all articles where a natural appearance of unpolished marble, biscuit china, or Pariah is required, and they are capable of being washed in the same way as ordinary biscuit china,']?arian, or unpolished marble, which they very much resemble.

Casts havingbeen thoroughly indurated and .dried as described may be treated by the process which forms the second part of the invention in order to render them still further impervious to Water and atmospheric changes. This second process consists in placing the casts in a bath of melted pure white wax,

- paraffine by preference, as this keeps its White ness better than any other. This wax I place in an ordinary bath, this bath being placed or standing Within a larger water-bath, which must be filled with hot or boiling water and kept up to boiling heat. The wax placed in the inner bath is melted by the action of the boiling water contained in the outer bath. During the whole time that any casts are immersed the water must be kept up to boiling heat and the wax in a molten state, or else the wax would get too cold, in which case the casts could not be effectually acted on. This, there- .fore, is of the greatest importance for the fu rther fulfillment of my invention. The length of time for immersion must vary according to the porosity and thickness of the articles to be treated-i. e., for casts one inch thick from fifteen minutes to half an hour would suffiee, Whereas casts measuring from six to twelve inches would require to be immersed in the hot wax from one to two hours,or even more.

The test for ascertaining whether the casts are fully permeated with the hot wax is this: If any article on being taken out of the wax bath has not received as much of the hot wax as it can absorb it will quickly appear to be dry on the surface; but if it is fully permeated it will drip, showing that the second process lutely necessary to keep the casts in the. wax bath until they are fully permeated; but for external decoration or use, also for molds, it is necessary on the score of greater durability that all casts, molds,or other articles should be fully permeated with the hot wax.

After the second process is completed and the casts are quite cold, those requiring to be polished are polished by the application of ordinary'soft soap and water rubbed on With a sponge or soft brush, and then well rinsed and rubbed dry. This polish is renewed stantially as described.

2. The process of treating plasterofparis casts or molds after immersion in solution of borax with white or paraffiue wax, substantially as described.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

EMMA THOMAS LAXTON CLARK.

. 'W'itnesses:

E. SORIVEN, ARTHUR E, EDWARDS. 

